Intercommunicating system and apparatus therefor



L. w. PARKER 2,189,269

Original Filed April 26, 1937 3 Sheets-Shet 1 INTERCOMIUNICATING SYSTEM AND APPARATUS THEREFOR Pet). 1940.

fw' J/M 3nnentor' V 1 Pl Eli Feb. 6, 1940. L. w; PARKER I 2,139,269

m'mxcouuumcmme SYSTEM AND APPARATUS THEREFOR Original Filed A rii 26, 1937 s Sheets-Sheet 2 TT T;

lnmmtor 5 Sheets-Sheet 3 I Feb. 6, 1940. L. w.' PARKER INTERCOMIUNICATING SYSTEM AND APPARATUS THEREFOR Original Filed April 26 19s? Iii Patented Feb. 6, 1940 STATES PATENT OFFICE INTEBCOMMUNICATING SYSTEM AND APPARATUS THEREFOR Louis W. Parker, Astoria, N. Y., assignor, by mesne assignments, to C. S. I. Development Corporation, New York, N. Y., a corporation of New York Original application April 26, 1937, Serial No.

138,894, now Patent No. 2,121,883, dated June, 28, 1938. Divided and this application May 24,

1938, Serial No. 209,855

Claims. (01. 19-1) I safety and reliability in signal communication is points.

attained.

Another object is to provide an improved method and means for coupling a plurality of signal reproducing devices such as loud-speakers or the like, to a transmission line whereby failure or abnormal conditions in one reproducer are of negligible effect on the other reproducers.

A further object is to provide a telephone intercommunicating system which is intended for use in situations where theextraneous noise level is very high, and wherein the telephone transmission line is required to carry audio frequency currents of large power amplitude.

A still further object is to provide an improved method and apparatus for controlling a signal call device in a telephone intercommunicating system.

A feature of the invention relates to the means for inductively coupling a loudspeaking signal reproducer or similar device, to a substantially linear shielded cable whereby increased coupling efliciency is attained.

Another feature relates to the means for inductively coupling a signal device to a telephone wire without breaking the wire and with a high degree of coupling efllciency.

7 Another feature relates to an improved circuit arrangement for controlling, from a central station, the local circuits of a plurality of signal reproducing devices inductively coupled to a transmission line at a plurality of outlying Another feature relates to a two-way intercommunicating telephone system wherein novel circuit means are provided to control the opera- I tlon ofa signal call or supervisory device at a central station when communication is desired therewith from any one of a plurality of outlyin stations.

A further feature relates to a novelrelay circuit arrangement for signaling systems, wherein the relay is designed so that its contacts remain in normal position even when the steady normal line current flows therethrough, but which operates its contacts when the line current is settling to its steady state from a higher value.

A further feature relates to a novel marginal relay and circuit whereby the relay operates its contacts only after a normally closed shunt around the relay is removed and during the interval the current through the relay is dropping to its normal steady state.

A still further feature relates to the novel organization, arrangement and relative connection of parts which go to make up a safe, reliable and eillcient two-way intercommunicating system peculiarly well adapted for use on ships and other locations having a high extraneous noise level.

Other features and advantages not specifically enumerated will be apparent after aconsideration of the following detailed descriptions and Fig. 1 is a schematic perspective view of the,

coupling arrangement according to the invention.

Fig. 2 is a schematic wiring diagram of a system embodying the principle of Fig. 1.:

- Fig. 3 is a detailed'schematic wiring diagram of a preferred form of pilot or loud-speaker control circuit.

Fig. 4 is a schematic layout showing one typical use of the invention aboard a ship.

Fig. 5 is a schematic wiring diagram of part of the system shown in Fig. 4, and embodying the principles of the preceding figures.

In certain types and locations of signal intercommunicating systems it is important that the signals be reproduced with sufficient volume as to be clearly distinguishable even in extremely noisy surroundings, for example aboard a battleship or the like. While this object can to a certain extent be achieved by transmitting the signal currents at low energy level over a line, and

amplifying them to the desired level at the receiving stations, this latter method is very costly because it requires individual sources of power and individual amplifiers at each of the receivlocations it is not advisable or convenient to have local power supplies. Thus aboard a ship it is highly desirable to have a central source of electric power and to avoid the use of separate power lines (as distinguished from signal lines) to each receiving point. Accordingly the present invention is concerned mainly, although not entirely, with a signal intercommunicating system where the signal energy is amplified to the requisite level at the central point and is transmitted at this high level to the several receiving points. Because of the heavy signal power carried by the line, it is important where a plurality of signal reproducers are coupled to the line, that abnormal conditions or undesirable interference at one reproducer, have substantially negligible effect on the other reproducers. While various proposals have heretofore been made whereby signaling devices can be coupled to a telephone line or to a cable, .these prior proposals have involved a physical or conductive connection to the wire or have required high amplification of the picked up signals in order to operate a loudspeaker or.

the like. These prior arrangements have been wholly useless where the line is in the form of a shielded or armored cable. I have found that it is possible to couple a plurality of signal devices to a shielded cable by using the shield to complete an inductive loop to act as the primary of a pick-up transformer which may be connected directly to a loud-speaking device or the like. Such an arrangement is schematically illustrated in Fig. 1 wherein a section of an armored cable carrying audio frequency currents, is shown. The numeral i represents a wire of the cable which is provided in the usual manner with an insulating covering 2 of any wellknown material, and also with any wellknown form of metal of metal sheath 3. This metal sheath may consist of an under layer of a metal wrapping overlaid with a continuous lead covering. As will be described in detail hereinbelow, the wire i and the sheath 3 form the conductors of a telephone or signaling pair, the current flowing through the wire I in the opposite direction to the flow through the sheath as indicated by the arrows. Ordinarily the sheath being parallel to and completely enclosing the wire, the resultant electromagnetic field would be substantially negligible so that a pick-up coil surrounding the cable would have substantially negligible signal voltage induced therein, and certainly not enough to operate a device such as a loudspeaker. However if the sheath is broken so as to produce a gap as indicated in Fig. 1 by the numerals and G, and the ends 5, 6 are connected by a wire loop 4, then this loop 4 together with the section of wire I between points 5 and 6, constitutes a complete inductive loop. Consequently if a suitable pick-up coil is located properly with respect to this complete loop, a substantial signal voltage will be induced therein. While the invention is not limited to any particular form of pick-up coil, it is preferred to employ a'coil comprising a split magnetic core as shown, comprising two abutting laminated sections 1, 8 to act as a closed transformer core, it being understood that a suitable casing may be provided for the core when the sections are'placed together and fastened in any suitable manner. A transformer secondary winding 9 of any desired number of turns is insulatingly wound around one leg of the core. The terminals I0, ll of this secondary winding may lead directly to any suitable form of 'signal reproducer, for example an electric loudspeaker or the like.- While Fig. lshows the sheath removed from a considerable length of the cable, it will be understood that this is not necessary so long as the sheath current is compelled in whole or in part to flow through the conductor 4. Thusas shown diagrammatically in Fig. la the sheath 3 is removed in a very narrow band, as for example by a special saw, and the resultant annular gap may then be filled or impregnated with a suitable insulating material to prevent direct contact with the wire I.

I With the foregoing arrangement I have found it possible by impressing the audio frequency currents on the wire I and sheath 3 at high current density, to produce at the terminals l0, ll sufficient signal voltage to operate a loudspeaker directly, i. e., without any local amplification between the pick-up coil and the loudspeaker.

Referring to Fig. 2, there is shown in generalized form a system employing a plurality of loudspeakers located at a plurality of receiving points supplied by a common cable. Thus a source of audio frequency waves l2 at a central station impresses the signal currents by means of a coupling transformer l3, on the cable wire 5 and the sheath 3. If desired, a key It may be provided to control the continuity of the line for purposes described hereinbelow. As indicated, the outer metal cable sheath is broken where it passes the receiving points or stations I i, l5, l6 and surrounding the gap at each station is a pick-up transformer ll having a secondary winding similar to that of Fig. l. The gaps in the sheath are bridged by conductors i to complete the primary inductive loops of the respective transformers. At the terminal of the cable the sheath 3 is connected by a wire l8 to the wire l thus completing the signaling circuit, and if desired this terminal of the circuit may be grounded as shown. The terminals it, ll of each transformer are connected to the winding id of a suitable form of loudspeaker 2E3.

In certain cases it may be desirable to have one or more loudspeakers normally'disconnected from the cable except when signals are to be sent thereto. This may be rendered necessary where the loudspeaker is located in a place where it is likely to pick-up as a microphone, local interfering noises. Such an arrangement is illustrated in Fig. 3, wherein one of the stations of Fig. 2, for example station I4, is shown in schematic detail. The pick-up transformer I! instead of being provided with a single secondary winding is provided with two secondary windings 2|,22. Winding 2| is preferably of high impedance and large number of ampere-turns, while winding 22 is preferably of low impedance and small number of ampere-turns. There are provided a pair of contacts 23 through which the loudspeaker winding i9 is connected to the winding 22, these contacts being controlled by a relay winding 24. For the purpose of energizing winding 24, it is connected in circuit with winding 2| through a low or audio frequency choke coil 25, to a full-wave rectifier arrangement'26, preferably of the dry or copper oxide type. The rectified output therefore controls the contacts 23, and when the powerful signal currents are not impressed on the cable wire and sheath, the contacts 23 are open and loudspeaker 20 is ineffective. When the signal currents of sufiicient power are impressed on the line, contacts 23 close and connect the loudspeaker in circuit. Instead of using the audio frequency signal currents currents may be superposed on a low frequency current, for example a 60 cycle alternating current, which latter is practically inaudible in the loudspeaker. The existence of this 60 cycle current on the line maintains contacts 23 closed. If for any reason contacts 23 should stick when not desired, there will be only aslight increase in the-noise level caused by device acting as a microphone, because of the low impedance of.

winding 22.

Fig. 4 shows a typical arrangement on board a ship, embodying the principles already described. The numeral 25 represents a central source of power supply, and numeral 26 represents the bridge or othercentral point of communication. The loudspeakers are arranged so.

that some are equipped with pilot circuits as disclosed in Fig. 3, while others are coupled to the cable as described in connection with Figs. 1 and 2. The former are represented in Fig. 4 by the circles 21, and the latter by the rectangles 28. The loops joining the gaps in the cable sheath corresponding to the loops of Fig. 1, are indicated by the numeral 23, while conductors 33, 3! represent the metal sheath of the cable and the cable wire respectively.

While any well known calling, supervisory and switching circuit may be utilized in the system of Fig. 4, it is preferred to employ an arrangement such as shown in Fig. 5. Merely for purposes of explanation it will be assumed that the loudspeaker 23e'alone is to be used for two-way communication, while the remaining loudspeakers are to be used for incoming messages only, as indicated by the contacts 23 corresponding to contacts 23 of Fig. 3. The control panel for the system is indicated by the dotted rectangle 32 and may be located at the bridge 23, while the remaining parts, except of course the cable and its coupled loudspeakers, are located at the central power room 25. The signaling line-circuit comprising the cable sheath and g the cable wire, is controlled by relays 33, 3d. Relay 3% is provided with an armature 35 and a pair of contacts 33, 3? which selectively connect either the incoming signal amplifier 38, or the outgoing signal amplifier 39, to the line. There is also provided a source 33 of low frequency alternating current, for example 60 cycles, which is applied to the line to control the contacts 23 as described in connection with Fig. 3.

At the control panel 32 there is provided a signal lamp ti which is lighted from the low voltage D. C., source 32 under control of con-' tests 33, at of relay it. The sourced? may be a 24 volt rectified and filtered power supply, one terminal of which is grounded as shown. The relays 33, 3d and 33 are designed to operate from a 24 volt source but may operate from a source as low as 8 bolts and as high as 48 volts. the purpose of controlling the various amplifiers and the light M, there is provided a switch hav- .ing two fixed contacts-t3, ii and a switch arm to. Contact M is grounded; contact 33 is connected to one terminal of the winding of relay 33, the other terminal of which is grounded; and the switch arm 33 is connected through the wind- I ing of relay 33' to the positive terminal of source relays remain deenergized.

For-

contacts of which are preferably shunted by a condenser 52.

When switch 43 is in its in position the circuits for relays 33 and 34 are broken and these It there are any audio frequency signals impressed on the line from a distant loudspeaker, for example loudspeaker 23c acting as a microphone, these cur-- rents flow. through the cablewire, condenser .53, contacts 54, 55, contacts 35, 36, primary winding 56 of inputtransformer il retuming thence by conductor 58 to the sheath 3, switch 51 to the cable wire. ne'cted to the input of asuitable audio frequency amplifier '38 the output'of which is applied to loudspeaker 50. Thus the messages may be transmitted through loudspeaker Me to loudspeaker 53.

The foregoing signaling circuit is complete if the person at the bridge has operated or left key 43 in its "in position. If the switch 'is in its off position when communication is desired with the bridge, then under these conditions a circuit exists from the positive terminal of source 32, coil 34, switch 48, contact 46, winding of relay 33 to ground.v Belay 33 thus stays operated and breaks the line circuit at contacts 54, 55. The operation of relay 33 also removes the shunt from the winding of relay 35, at contacts 50, 6t. While there existed previously a circuit from the positive terminal of source 32, resistance62, iron core choke 0011.63, winding of relay 35, cable wire I, switch 5! to ground, the relay-45 did not operate because of the shunt through contacts El, 62. Relay 35 is a marginal relay and will not normally operate by the steady state current which flows from source 32 in series with elements 32, 33 and winding of relay 35. However the instant the shunt is removed at contacts 63, 6!, the line current does not drop to its lower steady state value by inclusion of the windingof relay 33 in the circuit, since the choke coil 83 acts as an electrical inertia or storage device. In other words there is an appreciable interval of time required for the line'current to drop from its value with elements 32, 33 only in circuit, to its value with elements 32, t3 and 35 in circuit and during this interval the current is of sumcient magnitude to operate said relay 35. It will also be understood that relay 53 when operated is held operated by the final steady state current.

As long as relay 45 is operated, the circuit for lamp d! is broken and this lamp is unlighted. When the person at loudspeaker 23c wishes to attract the attention of the person at the bridge, the former momentarily opens switch 5 i, whereby relay 35 is immediately deenergized and remains released, thus closing the circuit for lamp it.

The person at the bridge noticing the lighted lamp, operates switch 38 to'either the "in" or the out position. In the former position relay 33 releases to complete the talking circuit from the loudspeaker 202 through contacts 34, 35 and contacts 35, 33, to the incoming signal amplifier 33 and the loudspeaker 53. In the latter position, relay 34 is operated thus completing the talking circuit from loudspeaker Me to the outgoing signal amplifier 33 and the microphone 39. It shouldbe noted that with respect to relay t5 and relay 33, that the contacts 63; 6| open to remove the shunt around relay 43, slightly in The secondary winding 59 i mentarily resulting in a click in the loudspeaker 20c each time the switch 5| opens and closes the circuit. Should by chance the switch 5| get out of order, the condenser 52 provides 'a path for I the audio-frequency currents. Likewise should the contacts of relay 33 get out of order, condenser 53 maintains the A. C. circuit. During any of these latter abnormal conditions, lamp 4| stays lighted as an indication of trouble.

While specific apparatus and circuits have been described herein, it will be understood that the invention is not necessarily limited thereto. For example the switching, supervisory and marginal relay arrangements of Fig. 5 are applicable to any type of signaling line and are not necessarily limited to a line wherein the cable sheath acts as a line' conductor. Likewise while the invention has been described in connection with a system of telephone communication, it will be understood that it is also applicable to telegraphic communication and the like. Various changes and modifications may be made in the disclosure with-- out departing from the spirit and scope-of the invention.

Serial No. 138,894, filed April 26, 1937.

What I claim is;

1. In a signalling system, thecombination of a signalling pair formed of a sheathed cable, the sheath of which forms one of the signalling pair, a transmitting station connected across said pair, a receiving station inductively coupled to said pair, a signal reproducer at said receiving station,

a relay for controlling the circuit of the reproducer, and means also inductively coupled to said pair to control said relay.

This application is a division of application 2. In a telephone system, a signalling pair formed of a conductor having a conductive sheath, the sheath forming one of the pair, a transformer winding coupled inductively to the pair by a loop formed in part of the said conductor and in part by an auxiliary conductor connecting gapped points in said sheath, a loud speaker in circuit with said transformer winding, a relay for controlling the continuity of said loud speaker circuit and another transformer winding also inductively coupled to said pair for controlling the continuity of the loud speaker circuit.

3. A- system according to claim 2 in which the first transformer winding is of low impedance and low ampere turns and the second transformer winding is of highimpedance and high ampere turns.

4. In a signalling system, in combination, a transmitting station, a receiving station, an armored cable extending-between said stations, a gap in said armor adjacent the receiving station, a conductor bridging said gap to form with the cable conductor a local conductive loop, a transformer winding inductively associated with said loop, a loud speaker having its winding in circuit with said transformer winding, and a relay controlledby signalling currents impressed on said cable conductor and said armor for controlling the circuit of said loud speaker.

5. A system according to claim 4 in which said second transformer winding is connected in circuit with an audio frequency choke coil and a rectifier.

LOUIS W. PARKER. 

